Power conversion device

• US 7,091,690 B1
• Filed: 09/30/2005
• Issued: 08/15/2006
• Est. Priority Date: 08/09/2005
• Status: Active Grant

• Current Assignee: Tmeic Corporation (Toshiba Corporation)
• Original Assignee: Toshiba Mitsubishi-Electric Industrial Systems Corporation (Toshiba Corporation)
• Inventors: Oka, Toshiaki, Kuroiwa, Akihiko
• Primary Examiner(s): DUDA, RINA I
• Application Number:
  US11/239,059
• Time in Patent Office: 319 Days
• Field of Search: 318/727, 318/807, 318/812, 318/254, 318/439, 318/138
• US Class Current: 318/727
• CPC Class Codes: H02P 1/029 Restarting, e.g. after power failure

Abstract

A power conversion device is constituted by: a power converter that receives AC power and uses this to drive an AC motor; a control section for controlling an inverter section of the power converter; a voltage detection section that detects the voltage of the AC power source; a current detection section that detects the input current of the AC motor; and a speed detection section that detects the rotational speed of the AC motor. The control section has a vector control section that converts the current detected by the current detection section into a torque current component and an exciting current component orthogonal thereto and respectively independently controls these, and, when an electrical quantity found from the voltage detected by the voltage detection section has dropped below a first prescribed value, reduces the instruction value of the torque current component in a prescribed ratio in response to the lowered electrical quantity and, when the electrical quantity has dropped below a second prescribed value smaller than the first prescribed value, reduces the instruction value of the torque current component to zero.

Claims

1. A power conversion device comprising:

a power converter that converts an AC of an AC power source to an AC with an arbitrary frequency so as to drive an AC motor;

a control section that controls an inverter section of said power converter;

a voltage detection section that detects a voltage of said AC power source;

a current detection section that detects an input current of said AC motor; and

a speed detection section that detects directly or indirectly a rotational speed of said AC motor,

wherein said control section comprises a vector control section that converts a current detected by said current detection section into a torque current component and an exciting current component orthogonal thereto and respectively independently controls said torque current component and exciting current component, when an electrical quantity found from said voltage detected by said voltage detection section drops below a first predetermined value, said control section reduces an instruction value or limiting value of said torque current component in a predetermined ratio in response to a lowered electrical quantity and, when said electrical quantity drops below a second prescribed value smaller than said first predetermined value, said control section reduces said instruction value or limiting value of said torque current component to zero.

4. The power conversion device according to claim 1, claim 2 or claim 3,

wherein said electrical quantity is an amplitude value of said voltage detected by said voltage detection section.

5. The power conversion device according to claim 1, claim 2 or claim 3,

wherein said electrical quantity is a value obtained by adding in a predetermined ratio said amplitude value of said voltage detected by said voltage detection section and an amount of change with time of said voltage detected by said voltage detection section.

6. The power conversion device according to claim 1, claim 2 or claim 3, further comprising

a voltage phase change amount detection section that detects an amount of change with time of a voltage phase of said voltage detected by said voltage detection section,

wherein said electrical quantity is a value obtained by adding in a predetermined ratio an amplitude value of said voltage detected by said voltage detection section and an amount of change with time of a voltage phase detected by said voltage phase change amount detection section.

2. A power conversion device comprising:

a power converter that converts an AC of an AC power source to AC with an arbitrary frequency so as to drive an AC motor;

a control section that controls an inverter section of said power converter;

a voltage detection section that detects a voltage of said AC power source; and

a current detection section that detects an input current of said AC motor; and

a speed detection section that detects directly or indirectly a rotational speed of said AC motor,

wherein said control section comprises a sensor-less control section that converts a current detected by said current detection section into a torque current component and an exciting current component orthogonal thereto and respectively independently controls said torque current component and exciting current component, when an electrical quantity found from said voltage detected by said voltage detection section drops below a first prescribed value, said control section reduces said instruction value or limiting value of said torque current component in a prescribed ratio in response to a lowered electrical quantity and, when said electrical quantity drops below a second prescribed value smaller than said first prescribed value, said control section reduces said instruction value or limiting value of said torque current component to zero.

3. A power conversion device comprising:

(1) a power converter that converts an AC of an AC power source to AC with an arbitrary frequency so as to drive an AC motor;

(2) a control section that controls an inverter section of said power converter;

(3) a voltage detection section that detects a voltage of said AC power source; and

(4) a current detection section that detects an input current of said AC motor;

wherein said control section comprises

(a) a frequency and voltage control section that controls an output frequency and output voltage of said inverter section in response to a frequency instruction; and

(b) an active current acquisition section that finds an active current from a current detected by said current detection section,

wherein when an electrical quantity found from said voltage detected by said voltage detection section drops below a first predetermined value, said active current or a limiting value thereof is reduced in a predetermined ratio in response to a lowered electrical quantity and, when said electrical quantity drops below a second prescribed value smaller than said first prescribed value from said voltage detected by said voltage detection section said active current or limiting value is reduced to zero.